In the telecommunications industry, connecting systems comprising an array of insulation displacement contacts (IDC) are typically used in telephone company central offices and the office buildings for electrical connection between cables and cross-connect wiring. These electrical connection systems are used throughout the telecommunications industry in order to interconnect corresponding wires in two sets of wires. The predominant connecting systems for building terminal cross-connect systems are currently the modular RJ45 connector system and the 110 connection system or variations of these connection systems. The modular type connector systems use a plug and jack type interface for making connections.
The RJ45 version of a modular connector system is a 4-pair connector system that cannot be broken down to smaller increments without wasting connector positions. A patch cord connection is made to a jack by deflecting a set of cantilevered spring wires in a jack with a mating set of fixed pressure contact surfaces in the plug, as the plug is pushed into the jack with a relatively low force. As the plug completes its insertion into the jack, it automatically latches with an audible click. By gripping the exposed back end of the plug, and depressing a lever, the latch can be released. The spring loaded wire contacts within the jack essentially push the plug out. The RJ45 modular systems have a panel with a flat front face. When a patch cord is installed, the cordage comes straight out from the panel. Cross-connect distribution rings bring the cordage back in along the face of the panel.
The 110 Connector System is designed with insulation displacement connections for both the cable connections and the cross-connect or patching connections. Therefore, a patching connection can be made by terminating cross-connect wires in the contacts IDC slots, or by inserting patch cord blades into those contact slots.
This Connector System forms a connector field that is front accessible, and is designed for wall mounting. Despite this design, the 110 system can be frame mounted, with the cables fed from the front in a manner similar to wall mounting. The cables can also be fed from the back of the frame. The front access is achieved by having a cross-connect field superimposed on a cable termination field; that is, superimposed on the cable routing. Cables are routed behind the wiring blocks, either in pre-mounted channels or between the rows of wiring block support legs. Cable ends are brought through their appropriate openings in the wiring block to the cable termination surface, and the exposed cable sheath is removed. The cable conductors are fanned out as twisted pairs to their appropriate termination ports in the index strips on the front face of a wiring block. Connecting blocks, which include contacts having insulation displacement portions on two opposite ends, are brought down and snapped onto the index strip to form electrical connections between the contacts and conductors. The front surface formed by the connecting blocks is the cross-connect field. A designation strip is placed between alternate rows and is used to label the conductor terminations on the rows on either side of it.
When a cross-connect field is intended for use with patch cords, 100 pair wiring blocks typically alternate with horizontal troughs, with patch cords from the upper 2 rows going into an upper trough, and patch cords from the lower 2 rows going into a lower trough. When a high percentage of patch cord positions are populated, the patch cord connectors present an unruly appearance and the labeling becomes very difficult to read, making cord location a time consuming process.
Patch cords in the 110 connector system have contact blades that make connection by inserting into the top IDC slots of the contact elements. The IDC are designed to remove insulation as it makes contact, and to achieve a high enough contact force to make a stable long term connection to unplated wire. Repeated insertions, of the patch cord blades, past this entrance geometry, with its high contact force, reduces the life of the patch cord blades protective plating. This contact force (about 2 pounds) holds the patch cord blade by friction and prevents it from sliding out by about a third of a pound per contact. The contact slots are tapered so any vibration or wiggling of the patch cord would cause the blades to slowly walk out of the slots, unless something else held them in place.
Connecting blocks may have hemispherical buttons that match mating holes in the patch cords. By putting on a mated patch cord, the side walls on the plug end flex as they slide over the connecting blocks' buttons, a snap-on/snap-off type of latch is enabled, and the plug end is disconnected. The force to overcome this latch and remove a 4-pair patch cord, with a straight pull, can be as high as 25 pounds. Removal can be effected by a side to side rocking of the patch cord. Because patch cord plugs are in close proximity to each other, removal of one patch cord can easily result in the dislodging of a neighboring patch cord. Therefore, technicians must be very deliberate and careful during cord tracing to avoid inadvertently dislodging a patch cord. Furthermore, the high friction on the connecting blocks' buttons can cause extensive wear of the surfaces so that the retention capability of the connecting blocks degrades after multiple insertions and removals.